1. Field of the Invention
The present invention relates to a display substrate and a method of fabricating the same.
2. Description of the Prior Art
A liquid crystal display, which is one of the most widely used types of flat panel displays, includes two substrates, on which electrodes are formed, and a liquid crystal layer interposed between the two substrates. In such a liquid crystal display, liquid crystal molecules of the liquid crystal layer are rearranged in accordance with voltages being applied to the electrodes. Thus the quantity of light passing through the liquid crystal layer is adjusted, causing an image to be displayed.
One of the two substrates described above is a thin film transistor substrate, which is an insulating substrate on which a plurality of interconnections are formed. A representative method of forming such interconnections is the photolithographic method of laminating component materials and patterning the component materials using a mask process. However, such a photolithographic method requires a number of processing steps, such as thin film deposition, photoresist spreading, mask alignment, exposing, developing, etching, stripping, and the like. The large number of processing steps can increase the process time and manufacturing cost for fabricating the thin film transistor substrate.
A liftoff method can be used to reduce the number of mask processes when fabricating the thin film transistor. In the liftoff method, the process of fabricating a thin film transistor substrate includes a process of removing a photoresist pattern of which the upper surface is covered with a conduction material, and the photoresist pattern and the conduction material formed thereon are simultaneously removed by the liftoff method.
In order to effectively remove the photoresist pattern using the above-described method, a sufficient undercut on the lower part of the photoresist pattern must be formed by etching a protection layer (sacrificial layer) positioned on the lower part of the photoresist pattern.
On the other hand, a portion of the interconnections may be formed in a multi-film (layer) structure, and if a relatively depressed film (layer) exists on one end portion of the multi-film (layer), a stepped portion may be formed on the protection layer that is spread on the upper part thereof This may, however, cause a problem in that an upper conduction layer (e.g., a pixel electrode) to be formed on the protection layer may be opened.